MRI of the Human Retina

Description

Diabetic retinopathy (DR), a complication of diabetes and the leading cause of blindnessin working-age adults, is a retinal disease whose prolonged course typically begins years priorto diagnosis. DR is presently diagnosed by clinical findings on examination; by the time theseare visible, significant irreversible damage to the retina has already occurred for most patients.Insufficient oxygen delivery and hypoxia associated with the energy-demanding photoreceptorshas been implicated in the early stage of the disease. Such oxygen delivery-utilization mismatchultimately precipitates late stage neovascularization and vision loss. We hypothesize that themismatch in oxygen delivery-utilization in the retina results in abnormal blood flow and tissueoxygenation in the early stage of DR before vision loss. Currently, there are no existing non-invasive imaging technologies available to detect these early changes, when intervention couldbe most effective. Imaging technologies that can detect early changes in blood flow andoxygenation could accelerate early detection of DR, offer focused screening of population atrisk, and enable longitudinal treatment monitoring. Early detection has the potential to preventblindness and improve treatment outcomes, including quality of life. Most existing retinal imaging techniques lack depth-resolved information (except opticalcoherence tomography for anatomical imaging) and rely on optical transparency which isfrequently hampered by media opacity (e.g., cataracts and vitreous hemorrhages). In contrast,MRI can provide anatomical, physiological, and functional data with lamina-specific depthresolution. Its application to the thin retina, however, has been challenging. Our grouppioneered multi-parametric, layer-specific retinal MRI in animals and has demonstrated someunique advantages. This proposal aims to take the first step to translate this innovativeapproach to study the human retina. Our central hypothesis is that: i) high-resolution MRI canprovide anatomical, physiological, and functional images of the human retina with laminarresolution, and ii) functional and physiological changes in DR patients will occur beforestructural abnormalities can be detected.